Some embodiments described herein relate generally to switch fabric systems, and, in particular, to methods and apparatus for using virtual local area networks (VLANs) in a switch fabric.
Some known switch fabric systems support multiple VLANs by adopting an existing standard that assigns a certain number of bits in a data unit header to specify a VLAN identifier. For example, according to the IEEE 802.1Q standard, 12 bits in the Ethernet header of a data unit are assigned to specify a VLAN identifier. The maximum number of VLANs that can be supported by such a known switch fabric system containing multiple switches, however, is the same number that a single switch can support. Thus, the availability of VLANs does not scale with the size of the switch fabric system. Some other known switch fabric systems support more VLANs by using more bits in the data unit header than defined in the existing standard to specify more VLAN identifiers. Such a method, however, is typically impractical because it changes the existing standard that is heavily in use for switch fabric systems.
Accordingly, a need exists for methods and apparatus that can increase the number of VLANs supported by a switch fabric system without changing any existing standard.